Hexokinase is an enzyme that obeys Michaelis-Menten kinetics. Draw a double-reci
ID: 533870 • Letter: H
Question
Hexokinase is an enzyme that obeys Michaelis-Menten kinetics. Draw a double-reciprocal plot for hexokinase using the data below: [glucose] V_0, no inhibitor V_0, with 5mM fructose a. Plot the data in double-reciprocal form below: (be sure to label the axes) b. What is V_max for the uninhibited enzyme? (be sure to use the right units) c. What is K_M for the uninhibited enzyme? (be sure to use the right units) d. If the amount of enzyme added was 0.200 nM, what is k_cat, for the uninhibited enzyme? e. What type of inhibitor is fructose? f. Does fructose bind to the same binding site on the enzyme as glucose? g. If you assayed the same enzyme with fructose alone (which has a lower affinity the glucose), would you expect the K_M to be greater or smaller?Explanation / Answer
Michaelis-Menten kinetics Equation is
V= VmaxS/(KM+S)
1/V= (KM+S)/VmaxS
1/V= (KM/Vmax)*1/S + 1/Vmax, this is the equation for double reciprocal plot
a plot of 1/V vs 1/S gives a straight line whose slope is KM/Vmax and intercept is 1/Vmax
the plot of 1/V vs 1/S is drawn and shown below
from the plot with no inhibition, the intercept 1/Vmax= 0.3, Vmax=1/0.3= 3.33 mM/min
KM/Vmax= slope = 0.039, KM=0.039*3.33=0.12987 mM
for inhibition Vmax=3.33 mM/min.since Vmax is same in the presence and absence of inhibitor, this is competitive inhibition.
Kcat= Vmax/ET= 3.33*10-3/(0.2*10-9)=1.7*107/min